1. Field of the Invention:
The present invention relates to a lens barrel having a double-sided printed circuit board loaded with electrical circuits.
2. Description of the Related Art
In recent years, automatic single-lens reflex cameras having a variety of functions such as auto-focus function are becoming popular. Interchangeable lenses to be used on such cameras also are required to incorporate electrical parts such as a focus detection motor, an electromagnetic aperture device and so forth. In consequence, electrical circuits mounted in such lenses are becoming large in scale and complicated in construction.
On the other hand, there is a trend for smaller sizes of camera bodies and interchangeable lenses, as well as requirement for packaging various complicated mechanisms in compact camera bodies and lenses. In consequence, only small spaces are available for the electrical circuits to be incorporated in camera bodies and interchangeable lenses.
In cameras and interchangeable lenses of the type described, therefore, electrical circuits are loaded in the form of printed circuit board having a flexible substrate to form an electrical circuit unit which is mounted in a small space, or gap, formed between an outer shell wall of the camera body and internal mechanisms.
For instance, a method of loading electrical circuit in a lens barrel has been proposed by the same applicant. This method will be described with specific reference to FIGS. 8 to 10.
Referring to FIG. 8, a first flexible printed circuit S board 101 and a second flexible printed circuit board 102 are shown in a state before mounting in a cylindrical housing 110 such as a lens barrel.
The first flexible printed circuit board 101 has a first main domain 101a and first connection domain 101b which is connected to a FIRST lead portion 101d leading from the first main domain 101a. The first main domain 101a is connected to an actuator (not shown) such as, for example, an aperture driving motor and a focusing motor, and is disposed in the axial direction of the barrel within the casing, i.e., in parallel with the optical axis.
The first connection domain 101b has a first connection pattern portion 101e for electrical connection to another printed circuit board and also has first locating holes 101c, and projects outside the housing 110.
On the other hand, the second flexible printed circuit board 102 has a second main domain 102a and a second connection domain 102b connected to a second lead portion 102d leading from the second main domain 102a. The second main domain 102a has a doughnut-like form and may carry electrical parts such as ICs, resistors, capacitors and so forth collectively denoted by 102f. The second main domain 102a is held on a step surface 110a which is orthogonal to the axis of the housing 110. The second connection domain 102b is provided with a second connection pattern 102e for electrical connection to the first flexible printed circuit board 101 and also has second locating holes 102c.
The second main domain 102a is mounted in the housing 110 so as to orthogonally cross the axis of the housing 110. In this state, the second connection domain 102b initially projects axially and outwardly of the housing 110 as shown in FIG. 9, so as to contact with the first connection domain 101b of the first flexible printed circuit board 101 at a position outside the housing 110. In this state, the first connection domain 101b and the second connection domain 102b are located by means of the locating holes 101c, 102c with the aid of a suitable jig which is not shown. Thereafter, the connection patterns 101e and 102e of both connection domains 101b and 102b are electrically connected by, for example, soldering as at 103. After the completion of the connection, the connection domains 101b and 12b outside the housing are bent inwardly of the housing so as to overlie the second main domain 102a as shown in FIG. 10.
Then, a lens mount 104 and a decorative sleeve 105 are mounted to complete the lens barrel.
This known arrangement, however, has the following disadvantages. Namely, the flexible printed circuit board 102 essentially has projected portions, 102b to 102e inclusive, because of the necessity for the mounting of the electrical parts 102f on the doughnut-shaped second major domain 102a. In consequence, the flexible circuit board in its developed state has a considerable size, resulting in a relatively high production cost.
The same applicant has proposed various related structures which pertain to mounting of a printed circuit board in a lens barrel and filed patent applications on such arts: namely, U.S. patent application Ser. No. 134,976 (filed Dec. 18, 1987); U.S. Pat. No. 4,596,454; U.S. patent application Ser. No. 239,263 (filed Sept. 1, 1988); U.S. patent application Ser. No. 274,959 (filed Nov. 22, 1988); U.S. Pat. No. 4,804,331; and U.S. patent application Ser. No. 136,346 (filed Dec. 22, 1987).